The objective of Core B is to provide histopathology support, both technical and interpretative, for Projects 1 through 4. For Project 1, Core B will process murine tissues for light microscopic analysis, for laser capture microdissection and for electron microscopy. Scoring of murine tissues for disease severity will be performed blindly. For Project 2, core B will provide diagnostic expertise to classify human renal biopsies as HIVAN vs. non-HIVAN renal disease by integration of light microscopic, immunofluorescence and electron microscopic findings in blinded fashion. For Project 3, novel reagents to gene products of interest will be screened on normal and diseased human renal tissue and murine tissues by immunocytochemistry and immunoelectronmicroscopy. For Project 4, immunohistochemistry for proteins regulated by Nef signaling Pathways will be performed on murine and human renal tissues.